Various approaches have been developed in the past for providing an article having elongated enclosed channels. Such channels are useful, such as for the circulation of fluids. Articles have been assembled having a plurality of discrete tubes bonded together, or to a common support structure. Additionally, holes may be machined into a solid block of material to form passageways. However, such constructions have been expensive to manufacture and have been difficult to construct with extremely small, and/or closely spared elongated passageways.
Electrodeposition of materials on patterns known as mandrels to construct articles having a desired shape has been known in the past. It is also recognized that electrodeposition onto a mandrel containing recesses or grooves may result in the formation of enclosed voids. That is, due to localized variations in the potential gradient during the electrodeposition process, the deposited material will form at a faster rate adjacent corners, projections or other sharp changes in the geometry of the mandrel. If allowed to accumulate at the tops of recesses of a mandrel, the material on each side of the recess will meet or "bridge" at an intermediate point over the recess, shielding the interior of the recess from the accumulation of further material. An enclosed void is thus formed, generally recognized prior to the present invention as a defect in the article produced.